1	package antlr.collections;
2	
3	import java.util.NoSuchElementException;
4	
5	/** A simple stack definition; restrictive in that you cannot
6	 * access arbitrary stack elements.
7	 *
8	 * @author Terence Parr
9	 * <a href=http://www.MageLang.com>MageLang Institute</a>
10	 */
11	public interface Stack {
12	
13	
14		public int height();
15		public Object pop() throws NoSuchElementException;
16		public void push(Object o);
17		public Object top() throws NoSuchElementException;
18	}
19